A wireless communication system has evolved in a direction for supporting a higher data transmission rate in order to meet an increasing data traffic demand.
Up to now, a wireless communication system has pursued a technology development in a direction of improving a spectral efficiency mainly in order to increase a data transmission rate, but it is difficult to meet an explosively increasing data traffic demand with this only spectral efficiency improvement technology.
One of methods for meeting this is to use a very wide frequency band. Since it is very difficult to secure a wide frequency band in a frequency band (<5 GHz) currently used in a mobile communication cellular system, a millimeter wave communication system operating in a higher frequency band that can secure a wideband frequency has emerged. However, since the millimeter wave communication system performs wireless communication in a high frequency band, a high wave path loss occurs. Accordingly, a radio distance becomes relatively short to cause reduction in the coverage.